The invention relates to an adjustment member for at least one device provided with a rotation shaft, for example to a mixing lever for operating at least one potentiometer,
with at least one lever which is fixed to a shaft journaled in a frame so as to be rotatable and which is connected by means of this shaft to the rotation shaft of the device in a mechanically non-positive manner, and PA1 with friction means acting under spring force. PA1 the shaft of the lever is journaled on both sides, in two support plates which are rigidly connected to one another, PA1 the friction means are arranged between the lateral surfaces of the lever and at least one of the support plates, and PA1 the spring force is active transversely to the operational direction of the lever.
Video programs are usually produced by means of a mixer which makes an output video signal from several input video signals. Input video signals can be faded in, faded out, or intermixed by means of a mixer, in dependence on the artistic effect envisaged. In a manual mixing process, a mixing lever is used as the adjustment member, comprising a potentiometer whose rotation shaft is connected to a shaft of the lever in a mechanically non-positive manner. A mixer comprises a plurality of such mixing levers, the potentiometer being arranged below the control panel surface and the lever being passed through a slot in the control panel surface, so that it can be operated by the operator. Operators of studio mixers impose high requirements on the mechanical properties of such mixing levers. It must be possible to carry out mixing/fading operations with pixel accuracy.
An adjustment member of the kind described above may comprise a lever for operating only one device or alternatively, for example, two levers for operating two devices. Accordingly, a mixing lever as described here may comprise one lever for operating only one potentiometer or alternatively, for example, two levers for operating two potentiometers, in which case the levers and devices, i.e. potentiometers, are coupled so as to form a unit.
In known mixing devices, the lever has a circular portion against which a resilient element is pressed. When the lever is operated, a more or less strong, adjustable force is exerted by the resilient element., so that the lever can be operated without play and without jolts. It has been shown that the friction surface of the lever becomes uneven in the course of time, so that the lever can no longer be moved smoothly but only in steps.